create_table(table_name, options = {}) public

Creates a new table with the name table_name. table_name may either be a String or a Symbol.

There are two ways to work with create_table. You can use the block form or the regular form, like this:

Block form

 # create_table() passes a TableDefinition object to the block.
 # This form will not only create the table, but also columns for the
 # table.
 create_table(:suppliers) do |t|
   t.column :name, :string, :limit => 60
   # Other fields here
 end

Regular form

 # Creates a table called 'suppliers' with no columns.
 create_table(:suppliers)
 # Add a column to 'suppliers'.
 add_column(:suppliers, :name, :string, {:limit => 60})

The options hash can include the following keys:

:id
Whether to automatically add a primary key column. Defaults to true. Join tables for has_and_belongs_to_many should set :id => false.
:primary_key
The name of the primary key, if one is to be added automatically. Defaults to id.
:options
Any extra options you want appended to the table definition.
:temporary
Make a temporary table.
:force
Set to true to drop the table before creating it. Defaults to false.
Examples
Add a backend specific option to the generated SQL (MySQL)
 create_table(:suppliers, :options => 'ENGINE=InnoDB DEFAULT CHARSET=utf8')

generates: 

 CREATE TABLE suppliers (
   id int(11) DEFAULT NULL auto_increment PRIMARY KEY
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8
Rename the primary key column
 create_table(:objects, :primary_key => 'guid') do |t|
   t.column :name, :string, :limit => 80
 end

generates: 

 CREATE TABLE objects (
   guid int(11) DEFAULT NULL auto_increment PRIMARY KEY,
   name varchar(80)
 )
Do not add a primary key column
 create_table(:categories_suppliers, :id => false) do |t|
   t.column :category_id, :integer
   t.column :supplier_id, :integer
 end

generates: 

 CREATE TABLE categories_suppliers (
   category_id int,
   supplier_id int
 )

See also TableDefinition#column for details on how to create columns.

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September 25, 2008
14 thanks

All methods

  create_table :table do |t|
    t.column # adds an ordinary column. Ex: t.column(:name, :string)
    t.index # adds a new index.
    t.timestamps
    t.change # changes the column definition. Ex: t.change(:name, :string, :limit => 80)
    t.change_default # changes the column default value.
    t.rename # changes the name of the column.
    t.references
    t.belongs_to
    t.string
    t.text
    t.integer
    t.float
    t.decimal
    t.datetime
    t.timestamp
    t.time
    t.date
    t.binary
    t.boolean
    t.remove
    t.remove_references
    t.remove_belongs_to
    t.remove_index
    t.remove_timestamps
  end
February 5, 2010
0 thanks

An alternate way to have a string ID as a primary key

You can disable automatically created primary key and add it to manually with mysql:

The migration file: 

  def self.up

    create_table( :my_special_table, :id => false ) do |t|
      t.string :id, :limit => 5, :null => :no
    end

    execute "ALTER TABLE my_special_table ADD PRIMARY KEY (id)"

  end

Then in a before_save filter you can generate the primary key for yourself.

Use a transaction and be aware of uniqueness!